Electrodeposition of nickel from an acid bath



Patented Apr. 12, 1949 ELECTRODEPOSITION F NICKEL FROM AN ACID BATH Henry Brown, Detroit, Micln, S gnor to The Udyllte Corporation, Detroit, Mich., a corporation of Delaware No Drawing. Application August 27, 1945, Serial No. 613,031

4 Claims. (Cl. 204-49) This invention relates to the electrodeposh tion of nickel from aqueous acidic nickel baths.

The object of this invention is to decrease the grain size and increase the luster and brightness of the nickel deposit without decreasing appreciably the ductility of the plate or the curto saturation in the baths, that is, they do notv have critical upper concentration limits.

The brighteners listed in Table I can be used in any type of operating acidic nickel baths with beneficial efiects. In Table II are listed by way of illustration a number of such acidic nickel baths.

The nickel plate obtained with the alpha and beta unsaturated aliphatic sulfonamides and sulfonimides present in the acidic baths is very fine-grained, of good color and ductility, and remarkably free from pitting. On buffed surfaces the plate obtained is at least as good in reflectivity and brightness as the base.

It is a remarkable fact, for example, that in a warm nickel chloride bath (bath No. 2-300 g./l. NiC1z'6H2O and 35 g./l. H3303) which gives very brittle darkish plate (evidently due to basic salt inclusions) at pH values of 4-5, the addition of about 4 g./l. of vinyl sulfonamide or allyl sulfonamide (added as the Ni salt) will produce very ductile fine-grained plate of good luster, brightness, and color, under otherwise the same conditions, i. e., temperatures, pH values, and current densities whereas 1,5 naphthalene disulfonic acid or m-benzene disulfonic acid will not accomplish this, and the plate is still very brittle and of poor darkish color, even though finer grained than the plain nickel chloride bath.

These facts also hold true in other high speed plating baths containing high nickel chloride concentrations, for example, 150 g./l. of nickel sulfate and 150 g./l. of nickel chloride. It is also interesting to note that formaldehyde at about 1 g./l. also gives brittle, darkish, finegrained, frosty plate in the high nickel chloride baths.

If other nickel brighteners such as, for example, zinc or cadmium in a concentration of about 0.1-0.5 g./l. are present in acidic nickel baths besides a sufficient concentration of a compound (or compounds) of Table I, the plate obtained is brighter than with either material alone in the bath. Also, the bath can tolerate larger concentrations of the zinc and cadmium than the plain bath without getting brittle, darkish, poorly adherent plate. This is also true with respect to thallous and mercuric salts in about the same concentrations. It is also true with respect to the impurity, copper, which does not produce any significant brightness when present in small concentrations, but tends, instead to very readily produce dark deposits, first appearing at the lowest current densities and extending upward as the concentration of copper is increased. In fact with respect to increasing the tolerance of the nickel bath to such materials which plate out preferentially to the nickel and tend at the slightest excess to discolor the very low current areas, vinyl and allyl sulfonamides. are extremely good. That is, they are very efiective for the very low current density values while at the same time being very effective in brightening for the middle to the very highest current density values.

While the beta unsaturated aliphatic sulfon amides (e. g., allyl sulfonamide) are similar in their effects in the nickel baths to the alpha unsaturated sulfonamide (e. g., vinyl sulfonamide), they diiier to a certain degree. The vinyl sulfonamide, forexample, makes possible a toleratlon of somewhat larger concentrations of materials (both inorganic and organic) which plate out preferentially to nickel and which when alone in the bath cause brittle and easily stained plate or poor color. Apparently, the beta oleflnic double bond as present in allyl sulfonamide does exert an efiect on, or transmits an eiiect to, the sulfonamide group and increases its reactivity, but not as strongly as does an alpha unsaturated bond. Apparently, conversely the sulfonamide group affects the active unsaturaaccacvv 3 tion characteristics of the alpha carbon double bonds more strongly than the more distant beta, that is, the beta double bonds are more strongly olefinic in character, and thus allyl sulfonamlde TABLE I Alpha and beta unsaturated aliphatic sullenamides and sulfonimides also exerts a brightening effect in a somewhat similar manner as does allyl alcohol, allyl amine, opwom allyl urea, allyl arsonic acid, and acrylic acid. The latter, however, do not increase the toleraan tion of impurities, in fact; they decrease the 1 CH 5 SONH tolerance. For example, in the high nickel F H chloride bath (e. g., bath No. 2), the addition e nu io amldel of allyl alcohol or allyl amine or sodium or nickel o1 acrylate from 1 g./l. to saturation onl produces finer grain but the plate is still darlf and very 2 (ma-lbs H brittle.

The alpha and beta unsaturated aliphatic sula onFe-s 0mm fonamides can be used with beneficial effects in H other acidic nickel baths, besides those listed a in Table II, for example, in baths made up with 4 nickel sulfarnate in whole or in .part. (Allylsulionamide) The best bufi'er as far as the cathode film is H H concerned is boric acid and is preferred, though E 1 other bufiers can be used, as, for example, formic, 5 H citric, or fiuoboric acids. tonvl ionamide) Mixtures of compounds of Table-I can be used H with beneficial effects (improved brightness of 6 CH l plate) as, for example, allyl sulionamide with H vinyl sulfonamide. Also mixtures of the compounds of Table I with aryl sulfonates, aryl sul- H fonamides, aryl sulfimides, aryl sulfone sultonic 3o acids enhance or improve the brightness of the 7 CHPJJCHPS plate. For example, 1-2 g./l. of o-benzoyl sul- H fimide with 0.1-1 g./l. of allyl sulfonamide. Also 8 0H J-s0=NHc.H 0,5 mixtures of vinyl or allyl sulionarnides or 5111- H H fonimides with vinyl or allyl sulfonic acids give ([2 (B beneficial effects. 9 2

Even concentrations as low as 0.1 g./l. of com- 501N131 pounds of Table I show beneficial effects over 10 A= M4 small ranges of current density, though in general at least 1 g./l. concentrations should be used. The 1 TABLE II I??? Bufier Other Salts TSHIIPDH DH 3885 3 Formula g./l. Formula g./l. 13 5? 0 300 45 3-6 10-00 7 s00 45 12s 5-100 2-6 10-60 8 15 Nmme NaCl 40 15 5.5 10-25 alpha and beta unsaturated sulionamides and sulfonimides such as the vinyl (ethylene) and allyl sulfonamides are very beneficial when added to acidic nickel baths containing from .1 g./l. to saturation of any one or more of the following: the naphthalene sulfonic acids, the benzene sulfonic acids, the benzene sulfonamides, the diphenyl sulfone sulfonic acids, in that the ductility of the plate and the brightness in the recesses (low current density areas) is improved. This is especially true ii. the chloride concentration of n such nickel baths is above 75 g./l. NiCl2.6H=O.

rate and nickel sulfamate, said solution also having dissolved therein an unsaturated organic compound selected from the group consisting of alpha unsaturated aliphatic sulfonamides and sulfonimides and beta unsaturated aliphatic sulfonamides and sulfonimides in a concentration suflicient to increase the luster and brightness of the nickel deposit and falling within a range from .05 gram per liter to saturation.

2. A bath for electrodepositing fine-grained, lustrous nickel comprising essentially an aqueous acid solution of a material selected from the group consisting of nickel chloride, nickel sulfate, a mixture of nickel sulfate and nickel chloride, nickel sulfamate, a mixture of nickel sulfamate and nickel chloride, nickel fiuoborate, a mixture of nickel fiuoborate and nickel chloride, 3. mixture of .nickel fiuoborate and nickel sulfate, a mixture of nickel sulfate, nickel chloride and nickel fiuoborate, and a mixture of nickel fiuoborate and nickel suliamate, said solution also having dissolved therein an unsaturated organic,

compound selected from the group consisting of vinyl (ethylene) sulfonamide and allyl sulfonamide in a concentration sufficient to increase the luster and brightness of the nickel deposit and falling within a range from 0.5 gram per liter to saturation.

3. A method for electrodepositing fine-grained, lustrous nickel comprising the step of electrodepositing fine-grained, lustrous nickel from an aqueous acid plating solution having dissolved therein and constituting the essential electrolyte thereof a material selected from the group consisting of nickel chloride, nickel sulfate, a mixture of nickel sulfate and nickel chloride, nickel sulfamate, a mixture of nickel sulfamate and nickel chloride, nickel fiuoborate, a mixture of nickel fiuoborate and nickel chloride, a mixture of nickel fiuoborate and nickel sulfate, a mixture of nickel sulfate, nickel chloride and nickel fluoborate, and a mixture of nickel fiuoborate and nickel sulfamate, said solution also having dissolved therein an unsaturated organic compound selected from the group consisting of alpha unsaturated aliphatic sulfonamides and suifonimides and beta unsaturated aliphatic sulfonamides and sulfonimides in a concentration sufficient to increase the luster and brightness of the nickel deposit and falling within a range from .05 gram per liter to saturation.

4. A method for electrodepositing fine-grained, lustrous nickel comprisingthe step of electrodepositing fine-grained, lustrous nickel from an aqueous acid plating solution having dissolved therein and constituting the essential electrolyte thereof a material selected from the group con sisting of nickel chloride, nickel sulfate, 2. mixture of nickel sulfate and nickel chloride, nickel sulfamate, a mixture of nickel sulfamate and nickel chloride, nickel fiuoborate, a mixture of nickel fiuoborate and nickel chloride, a mixture of nickel fiuoborate and nickel sulfate, a mixture of nickel sulfate,nickel chloride and nickel fluoborate, and a mixture of nickel fiuoborate and nickel sulfamate, said solution also having dissolved therein an unsaturated organic compound selected from the group consisting of vinyl (ethylene) sulfonamide and allyl sulfonamide in a concentration sufficient to increase the luster and brightness of the nickel deposit and falling within a range from .05 gram per liter to saturation.

. HENRY BROWN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

